The present invention pertains to seals for disposition between combustors and downstream turbine nozzles and more particularly to such seals which permit radial and axial movement between the sealed members as well as providing for cooling of associated members.
In order to enhance the efficiency of operation of gas turbine engines, which include combustors and turbines, it is necessary to provide an effective seal between the outlet of the combustor and the inlet to the turbine so that air from a surrounding cooling plenum cannot leak into the lower pressure area of the hot gas stream. The extreme temperatures associated with these portions of a gas turbine engine require that the seal employed be protected against thermal damage. In addition, the presence of thermal gradients throughout the combustor, turbine and seal materials, create a need for enhancing non-destructive relative spatial dislocation of the elements.
A further significant problem involved is related to vibration of the assembly. Uncontrolled vibration can lead to fatigue failure or at least to cracking of the combustor or turbine members or of the seal itself. Vibrational excitation is prevalent throughout this combination due to the aerodynamic effects of the extremely fast moving gas stream exiting the combustor. Therefore, means for preventing resulting vibration are necessary.
Certain prior art attempts at sealing the junction between the combustor and turbine have created further problems in themselves. For example, one type seal involves a circumscribing generally U-shaped member having one side of the U attached to a combustor liner and the second side attached to the sidewall surrounding the inlet nozzle to the turbine. The attachments utilized are rigid with respect to both sealed elements, and as a result have no means to reduce vibrational excitation or thermal expansion problems. In addition, the U-shaped member opening into the hot gas stream permits hot gases from the stream to reside within the seal for a significant period of time. Such residence can lead to thermal damage of the seal.
The current invention overcomes each of these problems in a simple and efficient fashion.